If either the membrane of a PEM fuel cell or SiC matrix of a phosphoric acid fuel cell or the seal of a fuel cell develops a leak that permits reactant cross over, so that anode fuel gas is mixed with cathode oxidant gas, the resulting heat from combustion of the fuel can become sufficiently high to affect adjacent cells, which in turn can affect additional adjacent cells, leading to the failure of an entire cell stack assembly by melting or cracking of seals, membranes and other components. Therefore, leakage between cathode and anode gases of even one single cell of a cell stack assembly cannot be tolerated.
Heretofore, any failed cell must be removed from the power plant. To remove the cell, the manifolds must be removed and the entire cell stack assembly has to be disassembled. If the failure occurs at the beginning of life of the cell stack assembly due to manufacturing defects, this may not be too significant. But if the failure occurs after extended periods of operation, releasing the pressure on the various cells can cause additional failure, such as the breakage of membranes which would otherwise remain operable.
The process of removing a cell by unstacking the cell stack assembly is time-consuming and expensive.
The prior art process of unstacking a fuel cell to remove a failed cell dictates that certain design features, such as adhesive seals, are not considered as appropriate, since the use of such features would inhibit the ability to remove a failed cell.